As with other Mr. King stories, he takes some idea too far, aiming for good, but learning from his friends about why it turns out to be not a good idea after all.  In this case, Mr. King likes flowers, but he doesn’t like when the caterpillars eat them, so he builds a machine to chase down and capture the caterpillar, only to learn that the smoke spit out my his machine and the plants it trampled were bigger problems, especially given that he neglected to ponder the benefits the caterpillar offers to the flowers once he turns into a butterfly.  So he turns his caterpillar-catching machine into a seed scattering machine that operates on smoke-free breath power.